Multiplex telephone system



Feb. 26, 1946. E. M. Dl-:LoRAlNE MULTIPLEX TELEPHONE SYSTEM 3 Sheets-Sheet 1 Filed Oct. 19, 1943 HSE F727? Afro/mmf Feb. 26, 1946. E. M. DELORAINE 2,395,467V

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MULTIPLEX TELEPHONE SYSTEM Edmond M. Deloraine, New York, N. Y., assignor to Federal Telephone and Radio Corporation, New York, `N. Y., a `corporation ofDelaware Application October 19, 1943, SerialfNo. 506,803

11 Claims.

This invention relates to multiplex communication systems and more particularly to communicationsystems using time modulated pulses to convey the wanted intelligence.

It has been proposed to transmit intelligence by a series of pulses,` modulated in time in accordance with the desired message. `A multiplex system of this type is shown in the patent to E. M. Deloraine and A. H. Reeves,

No. 2,262,838. In the patent, however, the synchronizing` system for assuring properly timed operation of the transmitters and receivers is onlygenerally indicated. Furthermore, no intermediate or kbranch terminals are provided, and two-way simultaneous transmission on the same line is not contemplated.

It is an object of my invention to provide a multi-channel communication' system with a novel method of synchronization and power supply.

It is a further object of my invention to provide a system for two-way pulse communication on a single transmission medium.

It is a still further object of my invention to provide a multi-channel pulse communication system wherein one or more of the channels may,

be terminated at an intermediate or branch circuit.

It is a still further object of my invention to provide means for supplying power to an intermediate repeater station from one terminal of a pulse communication system, With these objects and others in View the system according to my invention may include a pair of terminal stations interconnectedby a common line. At an intermediate' point in the line may be provided an intermediate or branch terminal which may be arranged to communicate with either or both the regular terminals over one or more channels. A power source at one terminal may furnish power at the intermediate terminal and to line repeaters in the line. At the same` time the energy from the power source may serve to synchronize operation of the transmitter and receiver equipment at the intermediate terminal and the other terminal of the system. In order to communicate simultaneously in both directions over the com mon line the signals may be carried in one direction by simple modulation of pulses, preferably in time, and in the other direction by a carrier frequency wave modulated by the modulated pulses. f

Other objects and features of my invention will become more apparent from the particular reference to munication system, with one terminal in Fig. 1,`

rectangles.' Lines I,

description of an embodiment thereof `made with the accompanying drawings, in which:

Figs. l, 2 and 3, taken together, illustrate schematically a complete multi-channel pulse `coina branch circuit repeater or terminal in `Fig,2 and the other terminal in Fig, 3. f r

Turning to the drawings, in Fig. 1 is umstratecii; terminal equipment I0 coupled over line I I and' through a repeater `I2 to the intermediate or branch terminal equipment I3, 'shown in Fig.2. The intermediate branch terminal I3 is coupled overY line |I and a repeater VIII "to the other terminalequipmentl, Fig. 3.

At terminal I0 are shown in full lines three terminal connectors I, 2 and 3 which may be coupled to two-Way transmission voice liniesover a selector switch, if desired. Additional .channels may be provided, as indicated bythe dotted .2 and 3 are lcoupled over hybrid coils IUI, |02, |03, each provided with balancing networks |04, |05, and 'I 06, respectively, to transmitting and receiving equipment preferably of the time modulated pulse type. On the transmitting vside hybrid coils IBI. |02 `and |03 `are coupled to the -input modulators IIl'I,I08 and |09, respectively, the outputs of these modulators being applied over band pass separating filter Il3 adjusted to pass the impulse frequencies, and high pass filter I|4 to line II. These modulators areseparately controlled in a known manner, by

. means of energy applied over line Illfrom a synchronizing source I I2 and the respective phase Shifters I|'|, I.I8, and IIS, so as to apply signals to filter I 3 in spaced sequence.

At I I0 is provided an alternating current `power source which should be well regulated `to maintain a constant frequency. The `frequency of tin alternating `current from :this power source is Ypreferably asubmultiple frequency .of the cadence frequency of the impulses transmitted from mod. ulators |01, etc. For example, if the cadence frequency of the impulses is 12 kilocycles, the power source may be 3000 cycles. It is clear that lower or higher frequencies for the power source may be provided, if desired. Energy from power source 0 is used tol control synchronizing source l|2- to producey the desired switching the modulators. A rectifier II! is also coupled to the output of power source I I IJ` and over line |50 is used to supply the operating power for the modulators |07, IilB and |09 aswell as for the demodulators |21, |28 and |29 and the group detector |35, to `be described later. Power control frequency for IIII is being terminated at VUnder these circumstances, signal' energy from from source IIO is also applied over low pass filter IIS to line II serving to supply the low frequency power for unattended repeaters, such as I2 and the intermediate channel repeater I3, shown in Fig. 2.

Line II, as shown, serves as a two-way communication line, the incoming signals to terminal I being supplied by way'of a carrier frequency sufliciently high to carry the signal bearing pulses. The incoming signal energy from line |I passes over high pass filter III and band pass separating mier |33, adjusted to pass the modulated carrier frequency to group detectorr |35. Group detector |35 serves to detect the impulsesv incoming over line II [and removes the carrier frequency therefrom. The output signals from group detector |35 are applied to demodulators |21, |28/and |29 which demodulators are then coupled to the input side ,of hybrid coils |0I, |02 and |03 and v-hence to line terminals I, 2 and 3. The proper timing of the demodulators for separating the incoming channels is achieved by energy from synchronizing source II2. This synchronizing energy is passed over a phase shifter II6 and line A|55 serving to compensate for the transmission time of line II and over individual phase Shifters |31, |30 and |39, which serve to segregate the various channels, to demodulators |21, |28A and |23. respectively.

In v-Fig..2 is shown an intermediate or branch terminal repeater. serving to select one or more of the channels incoming over line II from both directions. To line I I are coupled high passi-liter 2I4 and low pass filter 2I5 serving to separate the signal. frequencies and the low frequency power energy from line II. Band pass lters 2 I3 and 2:33, coupled over to separate out energy from terminal I0 and from terminal I respectively. Energy from the output of low pass filter 2I5 is applied tothe rectifier 2IIvwhich, in turn, supplies operating power to demodulator 201,V modulator 221, demodulator 22,8,fmodulator 208, synchronizing oscillator 2I2, and to,other modulators and demodulators, as requiredover lines 210, ergy from the output to synchronireA the operation of synchronizing control oscillator 2I2 which serves to switch into operation the modulators and demodulators in proper sequential order to select the desired transmission channel and to assure application of energy fromthe modulator to line II in proper timed relation for reception at either of the terminals I0 or I5 over lines 260, 26|, 262 and 263.

In order more clearly to explain the operation of my invention as applied to the `drop channel, we. may best trace through the transmission of a channel between terminal I0 and intermediate terminal I3. For this purpose, 4it may be assumed that channel I associated with hybrid coil the branch station.

|0| is applied to modulator |01 and over filters II-3 and II4 to line II. Upon reaching branch terminal I 3, energy from synchronizing oscillator 2|2l is supplied over phase shifter 2I1 to demodulator 201 so that demodulator 201 will be operated in proper timed relation to select channel I. Energy from this channelis applied to demodulator 201 over band vpass filter 2I3, and they incoming pulses are thus demodulated. The demodulat'ed pulses may carry with them ringing or other signaling energy as well as voice frequency energy. The output of demodulator 201 is coupled to low pass lter 240 and if ringing signal is present etc. At the same time, en-V of low pass filter 2 I5 serves high pass lter 2I4 serve e ergy from synchronizing oscillator 2 I 2. shifter 231 is adjusted properly to time the pulses ringing relay 244 is operated, intermittently closing contacts 245, and applying ringing signals to outgoing voice line 246. When ringing signals are not present, the demodulated voice signals are passed over high pass filter 24| to the input side or hybrid coil 242 and hence to line 246.

Incoming voice signals over line 246 are applied to hybrid coil 242 which is provided with balancing network 243 and from hence to pulse modulator 221. Pulse modulator 221 is controlled by phase shifter 231 also in turn controlled by en- Phase of` this channel to t into the return trains of channels for-suitable selection at terminal I0. These pulses from the output of modulator 221 are applied to carrier modulator 235 which serves to provide the carrier frequency for communication to terminal I0. The output from carrier modulator 235 is then applied over band pass filter 233 to line II and hence back over repeater I2 to terminal I0. This carrier energy is then passed over high pass lter II4 and selected by band pass filter |33 for application to group detector '|35 along with the other incoming signal impulses Yfrom line II. The proper signals for channel I are' selected in demodulator |21 by means of the control wave applied over phase shifter |31 and from hence to the input side of hybrid coil IDI and from there to line terminal I.

It can thus be seen that with this arrangement, communication may be established between terminal I0 and intermediate or branch terminal I3. Should it be desired to select a different channel for demodulation at 201 and modulation at 221, phase Shifters 2I1 and 231 may be adjusted by means of a common control 20| to provide application of the cotrol wave in proper timed relation to select the desired channel. To this end phase Shifters 2I1 and 231. are preferably made to operate in steps so that each step constitutes substantially the normal time displacement between pulse signal channels. Alternatively, the switching may be made at terminals I, 2 and 3, so that the desired voice line may be connected to a permanent trunking channel for branch terminal I3. The signals selected at the branch terminal also traverse the line to the other terminals but if desired the equipment there may be disabled under control of an operator.

rIfhe signals from terminal I0 after passing intermediate or branch terminal I3, may pass over a further repeater I4 and over line II to terminal I 5. Here are provided the high pass and low pass filters 3I4 and 3I5 which serve to separate the power energy from the incoming pulse signals. The power energy may operate through a synchronizer 334' synchronously to control a local power source 3|0. It is clear that, if desired, the

operating power could be the incoming power signals but it is preferable to provide the local power source 3|0.

The output of local power source 3|0 may be applied directly to the demodulators 301, 308, 309 and modulators 321, 320 and 329 and to group modulator 335. At the same time the synchronizing signals from synchronizer 334 may be applied to synchronizing source 3I2 which serves to control the switching into operation of the demodulators and modulators in proper timed relation over phase Shifters 3|1, l3I8, 3I9, 331, 338 and 339, respectively.

On the modulating side or transmitting side of terminal I5, an additional phase shifter 336 is provided to take care of the difference in transderivecl directly from mission time between the modulator and demodulator groups. The various channels from terminal I are thus selected at terminal I5 and applied over hybrid coils 30|, 302 and 303 provided with balancing networks 304, 305 and 306, respectively, to the separate voice frequency lines.

In order clearly to explain the operation of this system, the transmission of signalsfrorn` I toward I0 will be traced. We may assume now that the channel incoming over 302 is the one to be traced. The incoming signal energy from 302 is applied to modulator328, the output of this l modulator is then applied to group modulator 335 along with the signals from the other modulators. Modulator 335 serves to modulate a suitableparrier frequency with these pulses to separate these outgoing channels from the incoming modulated pulse signal channels. These signalsfrom modulator 335 are then applied over band pass iilter 333 and high pass iilter 3|4 to line The signals incoming over line II to the branch repeater I3 are applied to carrier detector 251 over band pass filter 233 and hence to demodulator 228 controlled by phase shifter 238. If phase shifter 238 is adjusted properly to select this channel, the energy is demodulated therein. rI'he ringing signal is segregated by low pass filter 250 serving to operate ringing relay 254 and ringing contacts 255 to apply to lines 256 these ringing signals. Voice signals are applied over high pass lter and hybrid coil 252 to the voice line 256.

In the return transmission from terminal I3 to terminal I5 voice signals incoming over line 256 are applied to hybrid coil 252 which is also provided with balancing network 253 to modulator 208. Modulator 208 is controlled by phase shifter 2 I 8 to produce the proper 'time spacing for the incoming pulse channel. The modulated impulses are then applied over band pass lter 2|3 to line II and over repeater I4 to terminal I5. The

incoming signals to terminal I5 pass over high pass filter 3M, band pass lter 3 I3 to demod'ulator 308 and from there to the input side .of hybrid coil 302.

Assuming the channel is not selected for dropping at intermediatefterminal I3, the impulses pass over line Ii and repeater I2 to terminal i0. Here the incoming signals pass over high pass filter |I4 and band pass lter |33 to group detector |35 where the pulses are reproduced. These reproduced pulses are then applied to demoduiator |28 and from there the demodulated signal is applied to hybrid coil l 02 in line 2.

It should be understood that lrepeaters I2 and I4 must be arranged suitably to pass not only the impulse energy and the carrier frequency but also the energy from power source H0. Accordingly, these repeaters cannot readily be made as simple pulse repeaters but instead may be straight linear repeaters. In any case it may be desirable to bypass the power energy about repeaters I2 and I4 by means of low pass lters 22 and 23, respectively.

However, it should be understood that at the same time some of this energy may be tapped off by rectifier arrangements similar to those shown at the branch terminal repeater for energizing the tubes within the repeaters. Thus, the system, as described, is admirably suited to the op` eration of unattended repeater stations where lo calizer power supply is diiiicult to obtain.

Likewise, it is clear that, if desired, separate transmission lines between terminals I0 and I5 may be used for opposite directions instead of using the carrier energy for the two way repeater operation. f

It is also clear from the description given above that the power source ||0 serves the double pur- Dose of supplying power at the repeater stations and of synchronizing operation of the terminal equipment at the branch terminals and at the far terminals of the system.

It should likewise be distinctly under-stood that' common transmission line interconnecting said, v

terminals, means at said rst terminal for producing a plurality of trains of impulses each representing a communication channel, an alternating power source for supplying energy'at'said first terminal, means at said first terminal for producing from energy of saidsource a control wave for timing the impulses of each channel to interspace said impulses in time spaced relation on said common transmission line, .means `for applying power energy fromsaid power-source to said line, a branch terminal having receiving means coupled to said common'transmission line between said iirst and second terminals,` and means at said branch terminal responsive to said power energy for energizing said receiving means, and selector means responsive to said power energy for timing operation of said receiving means, to` select a predetermined channel at said branch terminal.

2. A multiplex signaling System comprising rst andl second terminals with a two-way transmis-` sion system therebetween, each of said terminals having 'a plurality of stations, each station having a transmitting circuit and a receiving circuit, each transmitting circuit` having means for generation of a train of time modulated pulses representing. one channel of communication, control means at said first terminal to control the timing of the transmissionof pulses from stations thereoi` to sandwich the pulses together with a given timing characteristic between `successive pulses of the resulting train of channel pulses, means for applying said resultant train of channel pulses and energy from said control means to said transmission system for transmission to said second terminal, means at said second terminal responsive to energy from said control means to control the alignment of the'receiving `circuitsl thereof with the proper 'channel pulses from said rst terminal, and furtherto control the timing of the transmitting circuits of said second terminal for channel communication back to said first terminal, a branch terminal having one nr more stations each having a transmitting circuit and a receiving circuit, a line junction connecting said branch terminal to said two-way transmission system, and means for placing anyone of said channels of communication in service be tween any station of said first and second terminals and a station of said branch terminal.

3. The system delined in claim 2 wherein the means `for placing any one of said channels of given timing 'characteristic communication in service between any station of said first and second terminals and a station of said branch terminal includes means for determining at the branch terminal the pulse timing of any given channel, and means responsive to energy from said control means to time the transmittingand receiving circuits of a branch station in accordance with the timing of said given channel.

4. A .multiplex 'signaling system Comprising rst'and second terminals with a two-way transmission `system therebetween, each of saidvterminals having a plurality ofstations, each station having a transmitting circuit and a receiving circuit, eachv transmittingl circuit :having means. for generation ofya train of time modu-` lated pulses representingone channel of communication, a power Source of "alternating current waves at the rst terminal, control means at said first terminal timed by said alternating current waves to control the timing of the transmission of pulses from stations thereof to sandwich the pulses together with a given timing characteristic between successive pulses of the resulting train of channel pulses, means for transmitting alternating current waves from said source to said second terminal, means at said second terminal responsive to alternating current waves 'to control the alignment of the receiving circuits thereof with the proper channel pulsesirom said iirst terminal, and further to controlathe timing of `the transmitting circuits of saidlsecond terminal for channel communication back .to saidl rst terminal, `a branch terminal :having one or more stations each having a transmitting circuit and a receiving circuit, a line junction connecting said branch terminal tosaid two-'wayftransmission system, means for deriving energy fromfasa-id alternating current Waves to energize-'said transmitting and receiving circuits, means vresponsive to said alternating current waves for timing operation of said transmitting and receivingcircuits, and means for placing one of 'said-'channels of communication in service betweenf rany station of said iirst and second terminals and astation of said branch terminal.

5. A imultiplex signaling system comprising first andsecond terminals with a transmission line therebetween, a plurality of stations at said rst terminal, each station having a transmitting circuit, each transmitting circuit having means 'for generation of a train of time modulated pulses representing one channel of communication, a power source of' alternating current waves at the first terminal for energizing said transmitting circuits, control means at said rst terminal timed by said alternating current waves tocontrol the timing of the transmission of pulses from stations thereof to sandwich the pulses together with a between successive pulses of the resulting train of channel pulses, means for applying said pulses and energy from said source to said transmission line, means at said second terminal responsive to alternating current waves to control the alignment of the receiving circuits thereof with the proper channel pulses from said first terminal, a branch terminal 'having one or morestations each vhaving a transmitting circuit anda receiving circuit, a line junction connecting said branch terminal to said transmission line, means for deriving energy from said alternating current waves to energize said transmitting and receiving circuits, means responsive to said alternating current waves for timing operations of said transmitting andreceiving circuits, and means for placing lone of .said channels of communication in service between any station of said rst terminal and a :energizing said transmitting circuit, control means at said first terminal including a source of energy to control the timing of the transmission oi pulses from stations thereof to sandwich the pulses together with a given timing characteristic between successive pulses of. the resulting train of channel pulses, means for applying said pulses and energy from said source to said transmission line, means at said second terminal responsive to energy from said control means to control the alignment of the'receiving circuits thereoi` with the proper channel pulses from said rst terminal, a repeater in said line v-between said rst and second terminals, and means at said repeater for deriving power for its operation from said energy applied to said line.

7. A multiplex signaling system comprising irst and second terminals with a two-Way transmission system therebetween, each of said terminals having a plurality of stations, each station having a transmitting circuit and a receiving circuit, each transmitting circuit having means for generation of a. train of time modulated pulses representing one channel of communication, a power source of alternating ,current waves at the first terminal, control means at said rst terminal timed by said alternating current waves to control the timing of the transmission of pulses from stations thereof to sandwich the pulses together with a given timing characteristic between successive pulses of the resulting train of channel pulses, means for transmitting alternating current waves from said source to said second terminal, and means at said second terminal responsive to alternating current waves to control the alignment of the receiving circuits thereof with the proper channel pulses from said rst terminal, and further to control the timing of the transmitting circuits of said second terminal for channel communication back to said first terminal.

8. In a multi-channel communication system wherein a plurality of timed pulse trains each representing a separate channel and a power wave are transmitted from a given terminal station over a common medium; a second terminal coupled to said common medium means at said second terminal responsive to said power wave for energizing the circuits at said second terminal, and selector means timed under control of said power wave for selecting a pulse train representing a predetermined channel from said common medium at said second terminal.

9. In a multiplex signaling system wherein energy from a rst terminal comprising a multiple timed pulse transmitting circuit and a control wave source is transmitted over a common medium,-a second terminal coupled to said common medium comprising means for receiving said pulses and said control wave, means responsive to said control wave for selectively segregating the ypulses representing different receivedchannels,

a multiplex transmitter means, means for transmitting a plurality of pulse channels from said energy from a rst terminal comprising a multiple transmitter means and means responsive to said received control wave for timing the transmission of said pulses from said transmitter.

10. In a multi-channel communication system wherein a plurality of timed pulse trains each representing a separate channel and a power Wave are transmitted from a given terminal station over a common medium; a second terminal coupled to said common medium, means at said second terminal responsive to said power 'wave for energizing the circuits at said second terminal, and selector means timed under control of said power wave for selecting a pulse train representing a predetermined channel from said common medium at said second terminal, and means for adjusting said selector means to alter the selection of channels.

11. In a multiplex signaling system wherein timed pulse transmitting circuit and an alternating current power wave source is transmitted over a common medium, a second terminal coupled to said common medium comprising means for receiving said pulses and said -power wave, means at said second terminal responsive to said power wave for energizing the circuits at said second terminal, means synchronized in response to said power wave for selectively segregatingl 'the pulses representing different received channels, a multiplex transmitter means at said second terminal, means for transmitting a plurality of pulse channels from said transmitter means and means responsive to said received powerwave for timing the transmission of said pulses from said transmitter.

EDMOND M. DELORAINE. 

